1. Technical Field
The present disclosure generally relates to Z-wave network technology, and in particular, to a thermostat that joins a Z-wave network as either a primary controller or as a repeater that acts as a gateway for home automation.
2. Background of Related Art
Command systems for commercial building and residential automation functions are available using a range of technologies. Among numerous technologies currently in use are X10®, Z-Wave® and Zigbee® technologies. Z-Wave technology is supported by a consortium of users and product developers, who have promulgated a set of Z-Wave communication standards that available through Zensys and the Z-Wave Alliance.
Z-Wave is a wireless home automation protocol that operates in the 908.42 MHz frequency band. One of the features of Z-Wave is that it utilizes a type of network known as a “mesh network,” which means that one Z-Wave device will pass a data frame along to another Z-Wave device in the network until the data frame reaches a destination device.
A Z-Wave network comprises a primary controller (hereinafter “controller”) and at least one controllable device, known as a slave node, or more simply, a “node.” The controller establishes the Z-Wave network. The controller is the only device in a Z-Wave network that determines which Z-Wave nodes belong to the network. There can be only one primary controller in the Z-Wave network. The Home ID of the primary controller identifies the Z-Wave network. An example of a primary controller may be a portable remote controller or a thermostat.
The primary controller is used to add or remove nodes from the network. The process of adding or removing nodes, also known as inclusion/exclusion, requires that the controller must be within direct radio frequency (RF) range of the node that is to be added or deleted from the network. The user must interact with the controller and the device during this process. For example, to start the process, the controller and the device should be brought together in close physical proximity. Next, the controller is placed in an inclusion mode. Then the device is activated so that it will enroll in the Z-Wave network.
After nodes are added to the network, the primary controller is responsible for determining communication routes to nodes, based on feedback from every node that the controller adds to the network. Additional nodes can be added at any time.
The data communication protocol established in a Z-Wave network uses a 32 bit unique identifier called the Home ID to identify separate Z-Wave networks that may be in range of each other. An 8-bit identifier, called the Node ID, is used to address individual Z-Wave devices (nodes) in the same network. A Z-Wave node will only respond to Z-Wave frames containing the Home ID and a Node ID that has been assigned to the node. Nodes typically receive data frames and reply, if necessary. Nodes cannot host pre-configured routes to other nodes. Typically, nodes are devices that only require input (and report status if polled), and generally do not generate unsolicited frames.
A Z-Wave node is a device that replies to messages addressed to that node. In addition, any node that receives a data frame addressed to other nodes can retransmit the data frame, thereby acting as a repeater and establishing the mesh network functionality. A node must be in a listening state to act as repeater. Such nodes must have a utility source of power. To limit battery consumption, nodes powered by batteries will not practically be configured to act as repeaters. Repeaters in the Z-Wave network help to extend the overall range and robustness of the mesh network.
Examples of nodes are light switches and dimmers for home automation, sensors (such as motion detection), HVAC devices such as thermostats and environmental sensors, door locks (entry control), appliances such as refrigerators, microwave ovens, dish washers, dryers, etc., and energy management applications that monitor electric usage.
Nodes that send command messages to control other devices in the Z-Wave network are known as controllers. Controllers added to an existing Z-Wave network can become secondary controllers. Secondary controllers may include traditional hand-held controllers, key-fob controllers, wall-switch controllers and PC applications designed for management and control of devices in a Z-Wave network.